Method of modifying internal strains in metal objects



-@C. 29; 1932. 3 LANGENBERG 591234 METHOD OF MODIFYING- INTERNAL STRAINS IN METAL OBJIS S Filed NOV. 6. 1929 Patented Dec. 20, 1932 v UNITED STATES FREDERICK c. LANGENZBERG, 0E

UNITED STATES PEPE a FOUNDRY c CORPORATION or NEW JERSEY EDGEW PATENT OFFICE ATER PARK, NEW JERSEY, nssmnoia. To many, or BURLINGTON, NEW JERSEY, A

Application filed November 6, 1929. Serial No. 405,080.

It is well known that metallic castings and forgings are liable to have internal strains produced by the casting and forging operatlon or in some cases produced by the subsequent annealing and heat treatment of the,

metals and, in fact, in some cases by the operation of machining. These strains are sometimes so great as to resultin the disruption-of the metal object, either totally or in part, andfrequently so great as to bring about deformation of the metal object. F requently these deformations are not apparent until the metal object has aged. In other cases these deformations are not apparent until the metal object is in the process of being machined. In still other cases the strains are not apparent until the metal object is subjected to heat such aswould be encountered by valves subjected to high temperature service.

The object of my invention is to provide a method by which these internal strains in metal objects can be neutralized or so changed in character and amount that they are no longer liable to bring about undesirable results, and I have discovered that by subjecting the metal article, whether casting or forging, to a high pressure sim ultaneously applied to the entire surface of the metal object and which consequently does not tend to materially change the form of the object, the internal strains can be greatly modified and altered and practically for all useful purposes eliminated from the metal object or so changed incharacter that the remaining strains are no longer harmful and, in fact, in some objects maybe beneficial.

The pressures which I have employed in treating diflere'ntmetal articles have ranged from 3,000 pounds per square inch to 150,000 pounds per square inch, and the pressure necessary with any particular metal object to eliminate its internal strains or so greatly modify them that they areno longer injurious will depend upon the metal and the shape of the article. In general, metals having a higher elastic limit and tensile strength.

will take more pressure to bring about the desired result rather than metals having a lower elastic limit and tensile strength. The optimum pressure can readily be determined with regardto any specific article and when once determ ned will be found applicable to all articles of the same material and construction. Hydraulicpressure is the most available and convenientmeans of applying the necessary pressure to the entire surface of the metal body.

While the optimum pressure applicable to any metal casting or forging can only be ascertained by experiment and trial, it is my experience that all metal objects have their internal strains relieved and are less likely to deformation or disruption by subjecting them to a pressure of from 3,000 pounds to 150,000 pounds per square inch of surface, and although metals having low elastic limit and tensile strength have not been treated in any extensive way, it is obvious from the observations made that pressures lower than 3,000 pounds per square inch can be employed in order to produce the desired results. or many objects where it is not necessary to determine an optimum pressure I would recommend a pressure of 75,000 pounds per square inch.

The drawing forming part of this specification illustrates an apparatus adapted for use in the practical application of my process of subjecting metal objects to suflicient pressure to beneficially modify the internal strains existing in the metal. The drawing is a sectional elevation of a convenient apparatus in which A indicates a container, which of course must be of suflicient wall strength to resist the pressure to which it is subjected. B indicates a passage for liquid under pressure leading to the container and connected with an accumulator diagrammatically indicated at C. D indicates a closure adapted to be seated and firmly held against the open end A of the container. E indicates a cage removably located in the con--- 7 tainer and adapted to support the objects to be subjected to pressure. Such objects supported in the cage are indicated at F, F.

In operation the metal objects to be treated are inserted in the container either in the cage or in any other convenient way. The closure D is then firmly secured over the open end of the container and liquid from the accumulator is permitted to flow into the container in which it will envelop the metal objects and subject them to the pressure provided by the accumulator. The structural chan' produced in the metal objects by the liqui pressure to which they are subjected occur very rapidly so that after a short exsure to this pressure the pressure can be relieved, the closure opened and the metal objects removed.

t will be obvious that my rocess in no wiserelates to the casting or orging operation by which form is given to a metal object but has to do exclusively with the treatment of previously formed forgings or castings for the purpose of relieving internal strain conditions found to exist in the casting or forging and it will also be obvious that my method does not involve any heatinglof the objects under treatment;

' aving now described my invention, what I claim as new and desire to secure by Letters Patent is: I J

1. The method of modifying injurious strains in the bod of previously, formed metal castings and orgings which consists in ascertaining experimentally a degree of pressure which will advantageously modify internal strains existing in the metal object to be treated and then subjecting such metallic bodies to such determined and known high pressure simultaneousl exerted on all parts of the body as will 'a vantageously modify :5 the internal strains thereof without materially changing the form of the body.

'2. The method of claim 1 as carried out with the application of hydraulic pressure.

3. The method of claim 1 as carried out 40 with hydraulic pressure in excess of 3,000

pounds per square inch.

45. The method of claim 1 as carried out with hydraulic pressure of approximately 75,000 unds per square inch.

'45 5. e method of claim 1, as carried out with the agsgcation of determined pressures between 3, pounds and 150,000 pounds to the 5%1518 inch. 6. e method of claim 1, as carriedout with the application of .determined pressures. between 3,000 pounds and 150,000 pounds tothe 31mm inch,-in which hydraulic pressure is us v FREDERICK C. LANGENBERG. 

